Assigkktob to the geasselli gheb iical



sept. 14 1926. 1,599,467

W. G. GRAVES APPARATUS FOR DRYING AND HEATING Original Filed Jan. 5l. 1923 (All/111114 Patented Sept 14.4, 1926.

UNITED STATES i mean-ii PATEN'l liltllld,

'l/ALTER Gu GRAVES, OF CLEVELAND OHIO, ASSIGNR LTO THE GRASSELL CE'IEBCAL CMPANY, OF. CLEVELAND, @rfi C1, CURPGRATION UEE APPARATUS FOR DBYNG- AND HEATNG.

.application filed January 31, 1923, Serial No. 616,107.

The invention relates to the drying` or heating; or the drying and heating ot materials, and particularly to the continuous treatment olf materials which heretofore it has been possible to dry or heat only in a non-continuous manner.

In the heat-treatment ot certain classes ot materials, for example liltenpress cakes, lithopone green cake, etc., itis practice te ct- `feet this in stationary shelf-driers by the aid et direct or indirect heat. It is common practice to separately dry materials in stationary pan driers with direct or indirect heat and subsequently dump the dried materials from the receptacles or trays in which they were dried and then to transfer the dried materials into heating apparatus,1nore commonly known as mutlling furnaces., which are' usuallyihand-operated, and there heat the materials while lying in a quiescent state, except tor occasional `stirring by means ot hand-operated paddles or bars, for a definite period oit time at a specific temperature. fitter such treatment, the materials 4re usually withdrawn trom the :furnaces by hand into quenching apparatus wher-e they are quickly drowned in water to prevent oxidation,

It is well recognized in the industry that the above operation is not entirely etlicient. ln the usual hand inutile, above referred to, the material to be mutlled with the exclusion ot air, is unevenly heated. That porn tion ot the material that touches or lie-s in close proximity to the hot floor or walls of the muiile and also that portion ot the charge that is most directly exposed to the heat radiated from the root ot the mulile may be excessively heated while other portions may receive un insuliicient amount ot heat or at least a considerably smaller amount ot heat than the aforementioned portions. Continuous stirring` or frequent intermittent stirring is out ot the question since entrance of air through the doors would cause oxidation and would detrimentally atlect the quality oit the material. `No satisfactory compromise by which sutlicient stirring with exclusion of air may be eifected, is possible bythe old inode ot operation'above mein tioned.

lit is the primary object ot' the invention to provide an apparatus for and a mode ot heat-:treating material .of thetype above re- Renewed January 22, 1929.

tei'red to in a continuous manner in such a way that the material is substantially uniformly exposed to the available heat` while air is substantially excluded.

It is another principal object to provide an `apparatus by which the operations ot' preliminarily drying and of subsequently heating; the material may be carried out economically at the same time in a continuons manner.

The invention will be more clearly under stood by reference to the acconipanyingD drawing, the single ligure of which represents a vertical sectional view, somewhat diagrammatic in certain respects, ot one embodiment of the furnace;

In the drawing is illustrated a furnace resemblinn` in a general way certain welllmown types of ore roasting` and calciniul furnaces. The Afurnace which may be cylindrical is provided with a combustion chamber l suitably connected in a well known manner by dues with a series ot lire-lines Q, 3, 4t, which with the combustion chan'iber serve to heat the material compartments or shelves 5, 6, 7 and the auxiliary shell' 8, respectvely.

Each of the heating` compartments is provided with rabbles 9 which ralre the mate rial under treatment and effect its pro rcssive movement from the top or the fn nace to the bottom, as is well understood in the metallurgical industry. Thus the material fed at the center onto the shelf 7 through the chute l() and is moved outwardly across the sloping;1 shelf by the rabhles to` the peripheral passages il through which it descends to the shell or compartment tl The rabbles in this compartment advance the inaterial toward the center chute 12 whereby it is transferred to the compartment 5, and so on until the material is finally discharged 'trom the furnace as by means of chutes lo.

The rabble-arms are connected to a hollow rotatable tube let disposed centrally of the furnace, and the tube is rotated at the dcsired speed through suitable driving mechanism indicated generally at l5 and a connecting tubular support 16.

Suitable glands or stutiing-boxes 17 are provided at the top and bottom between the rotating tubeand the stationary parts ot the furnace.

Air, or in some instances a neutral. or even I a reducinggas, is admitted to the tubefla at ery of the shelf 8 and is continuously ad.w

vanced to the central chute l() whereby it is introduced into the furnace proper, as above indicated'. The heated air or gas rising through the tube le is propelled by a blower through pipes and 23 to the shelf 8, and is removed at the opposite side through the stack 24.

llumeral 25 indicates a suitable quenching-tank which may be provided with a stirrer 26 and a lie-vel controlling float 2T.

.Part or all of the gases may be Withdrawn from the heating compartments, and for this purpose suit-able outlets 28, 919 are provided.

in the use of the apparatus described, for example for the drying'and heating of green lithopone containingusually about 40% iva-ter, the material in- Wet, sticky condition is fed continuously to the outer edge of the auxiliary shelf 8 and is advanced toufard the cent-er chute l() by the revolving rabblcs. During its passage across the shelf the ruw lithopone is subjected to hotv gas introduced through pipe 23. This operation serves to dry the material, or lithopone in particu lar, and enables the lithopone to be fed directly to the calcining chambers in a dry condition and Without access of air,' the muffies of the furnace bei-ng preferably kept. under a plus pressure to prevent entrance of air from the outside. Arriving on the hearth 7 the rabbles 9 rali'e and distribute the material and move it progressively to the peripheral chutes ll which convey it to the outer edge ofv the shelf next below across which itis advanced by the rabbles 9 to the center chute l2, and so on until the lithopone has traversed all of the heating compartments when it is finally discharged through the chutes 13 into one or more quenching-tanks. 25.

lt Will be understood that the number of Y shelves may be varied to meet the requirements of the particular use of the apparatus and that other details may be variously and considerably modified. u

rEhe proposed apparatus and method malte it possible to more completely prevent the access of air and oxygen to the interior of Vthe inutile since the rabbling is done without the necessity of .opening any doors. it further prevents mate-rial from becoming `o iis-heated locally on account ofthe mass off material the m'ue being 'constantlylessee? moved and mixed by the rabbles so that no portion of the mass remains in the hotter lo calities of the furnace long enough to become superheated. lt also Iaccompli.f-shcs a very tnorough mixing, thereby improving the evenness and bettering the quality of the material by making it thoroughly homogc neous so that in the product from this apparatus there is no over-roasted or Segre gated i-nateri-al which would malte the product locally fury in chemical or physicol properties.

ythe apparatus is particularly :ulvantugeous for handling material which requires the exclusion of air from the heating chambers during the heating operation7 such is the case with lithopone. llVhere a combination drying and heating operation is curriecl out, the auxiliary shelf provides an ei .ficient and highly economical means of reducing the moisture content of the -u'ct .material fed to. the furnace.

l am fully aware that the type of furnace means of Which I carry out the objects of the invention is generally Well known and do not claim any novelty in regard to the details of the furnace proper. l have selected this type. of furnace merely because it is particularly ivell adapted for the purposes of the invention. rl`he salient feature of the invention is the arrangement and the mode of operation by which air is substun tially excluded from the material in its pas-- sage fromv the drying chamber ll) through the inutiles. below it.

Claims:

l. Apparatus for drying und heating' wot material, comprising a substantially closed heating chamber, means for passing the material through the chamber, means in cluding a gas passage in thermal contact vvith the heating chamber for missing u hot gas into contact with the material. before the latter enters the heating chamber, under conditions preif'enting flou' out' air into the chan'ilier.

2. Apparatus for drying a :il heating u'ct material, comprising a closed furnace having an inlet at the top and an outlet near the bottom, a prclin'iinary heating chamber connected to the inlet, means for passing material successively through the preliminary heating chamber and the furnace and means including a gas passage in thernml contact with the furnace for passing a hot gas through the preliminary hating chamber under a pressure greater than atmospheric pressure.

3. A furnace for the drying and heatingx Wet material comprising a furnace of thc multiple closed hearth, revolving rabble type including a plurality of superposed closed heating chambers in series relation means .nil

defining a gas heating passage through the t furnace for preheating a ges out of. contact with the material, means for drawing gas from said passage into the uppermost heating chamber and means for withdrawing gases from the said uppermost heating chamber at such a rate as to maintain a positive pressure in the chambers of the furnace.

4. A furnace for drying and heating Wet material, comprising a. furnace of the multiple closed hearth, revolving rabble type including a drying hearth and a plurality of superposed closed mutlles below the said hearth and in series relation therewith,

means defining a gas heating passage through the furnace for preheating a gas out of contact with the material, a gas outlet from the drying hearth Zone and means hetWeen the Said passage and the drying hearth for forcing the preheated gas over the material thereon and through the outlet.

5. Apparatus according to claim l, includ ing means for quenching the hot material in a liquid Without access of air.

In testimony whereof, I aiiiX my signature.

WALTER Gr. GRAVES. 

